D10A is designed for a soft, wet, tacky track
condition.
D20A is slightly tougher than the D10A and works well on crumbs or
marbled tracks.
D30A is tougher than the D20A and performs well on cleaned off,
dry-slick tracks.
D50 is designed for hard, abrasive tracks that take rubber and require
grip.
D55 is designed for the same track conditions as the D50, but it will
be tougher and have less grip.

Every
Hoosier race tire has a four character serial code embossed into ONE
sidewall of the tire (example: J7B9). To be consistent when mounting
from set to set, the tire should be placed on the rim so that the
serial code faces towards the left side of the vehicle. This applies
to tires without directional arrows. On tires with directional arrows,
please mount the tire onto the rim so that the tire travels in the
direction of the rotational arrow.

Once the tire is on the rim, we recommend placing
the tire inside a mounting ring and adjusting the ring to fit snug
around the tire. We highly advise using the mounting ring as we
believe not using it can over stretch the carcass leading to
inconsistent sizing. Never exceed 40 psi to seat beads.
Once the tire has seated onto the rim, it is important the tire be
initially stretched to about 10 psi over cold starting pressure to get
the tire to its proper "profile". The tire should be set at
this pressure for a few minutes and then dropped to the desired race
pressure. The max inflation pressure is 57 psi (4.0 kg/cm2).
Never exceed the max inflation pressure under any circumstance.